1. Field of the Invention
This invention relates to a novel liquid crystal compound and a liquid crystal composition containing the same.
2. Description of the Prior Art
The display modes of liquid crystal display elements utilizing the optical anisotropy and dielectric anisotropy of liquid crystal compounds include various modes such as those of TN type, DS type, guest-host type, DAP type, White-Tailor type, etc., and the properties required for liquid crystal compounds used vary depending on the respective modes. For example, depending on the kinds of display elements, liquid crystal compounds having a positive dielectric anisotropy value or those having a negative one are required or those having an intermediate value therebetween are suitable. Further, it is necessary for liquid crystal compounds to exhibit liquid crystal phases within a temperature range as broad as possible, and also to be stable to moisture, heat, air, light, etc. At present, however, there is no single compound which satisfies all of such conditions, and several kinds of liquid crystal compounds and if necessary, non-liquid crystal compounds have been blended for practical use.
Recently, liquid crystal display elements operating within a broad temperature range i.e. over a range from low temperatures to high temperatures have come to be required more and more. Further, liquid crystal compositions having a large positive dielectric anisotropy value (hereinafter abbreviated to .DELTA..epsilon.) as a liquid crystal material and capable of a greater reduction in the threshold voltage and saturation voltage required for driving display elements have been desired. Still further, since liquid crystal compositions having a large optical anisotropy value (hereinafter abbreviated to .DELTA.n) can be used in a liquid crystal cell having a reduced distance between the substrates thereof, there is an advantage that the intensity of the electric field applied to the liquid crystal material can be increased even under the same impressed voltage; hence compounds having a large .DELTA.n have been required.
The object of the present invention is to provide a liquid crystal composition suitable for the above uses and a liquid crystal compound as a component thereof increasing the .DELTA..epsilon. and .DELTA.n of the composition.